Paper manufacture



Patented Aug. 1, .1933

UNITED STATES PATENT OFFICE 1 PAPER MANUFACTURE Harold Robert Rafton, Andover, Mass., assignor to Raifold Process Corporation, a Corporation of Massachusetts No Drawing. Application August 26, 1931 Serial No. 559,594

23 Claims.

- the same.

An important object is to provide a process for the reduction of the deleterious effect of alkaline filler on sizing in alkaline filler papermixes, I

A further object is to provide a process for the prevention or diminution of foam in the manufacture of both sized and unsized'papers filled with alkaline filler.

Other objects and advantages of this invention will become apparent during the course of the following description.

In the manufacture of paper filled with alkaline filler the alkaline filler acts upon certain acidic constituents, or effects thereof, in the paper mix with the result that such constituents or effects are substantially deteriorated even to the point of destruction. For example, size precipitates are thus acted upon asis also alum and the effect thereof in a paper mix. This action of the alkaline filler results in the deterioration or destruction of the sizing in sized papers. It results also in the destruction of alum and the effect thereof in unsized papers, with the result that serious foaming sometimes occurs on the paper machine and with the further result that troubles occur in the running of the paper due to tendency of the web to adhere at the dandy roll, presses, and the like.

In numerous of my patents and copending applications I have described a principle by the application of which this destructive action of alkaline filler can be greatly lessened if indeed not substantially avoided in the papermaking operation. This principle may be briefly termed, for convenience, the minimizing principle, that is, the principle of minimizing the time and/or intimacy of contact of the acidic constituent or constituents of the mix with the alkaline filler.

This principle is applied by the addition of one or more of the chemically incompatible ingredients late in the papermaking process, such as at the dilute stage, or even in some cases in the forming or to the already formed web.

I have found that there is another influence which markedly affects the action 'of alkaline filler on the acidic constituents ofamix, and that is, the temperature. I have found that the higher the temperature of a fibrous mix during its preparation and up to the point where it has completed its travel over the web-forming end". of the paper machine, the more marked is the deleterious action-of alkaline filler in said mix 3 I on acidic material or the effect thereof. I have found, moreover, that this deleterious action may 0 be greatly retarded, if not for practical purposes substantially eliminated, by diminution of the temperature.

I have found further that this principle of lessened activity of alkaline filler at lower 'temperatures may be usefully and practically applied by employing suitable means to minimize the temperature of the fibrous mix during its prep-- aration, up to the point where it has passed over the web-forming device of the paper .machine.

In the preferred practice of one adaptation of my invention I apply suitable refrigerating means to maintain-the fibrous mix in the beater, chests, and web-forming end of the paper machine at a temperature substantially lower than ordinarily maintained in papermaking practice. For this purpose I may employ artificial refrigeration for the water and other liquids going into the system as well as for one or more of the fibrous components. By the utilization of properly insulated beaters, chests, and other paper making equipment and apparatus, up to and including the web-forming end of the paper machine, a low temperature is maintained with little or substantially no rise due to abstraction of heat from the surroundings. Whereas I do not limit myself to the temperature to be maintained I have found that a temperature in the neighborhood of 10 C and not substantially higher, is a convenient one at which .to carry out my invention, although temperatures substantially lower are evenmore satisfactory.

In another adaptation of my invention it is possible, and in certain cases desirable, to carry out my process merely by keeping the fibrous mix in refrigerated condition throughout the concentrated stage, that is, in the beater and/or chests, allowing the dilute mix handling. instrumentalities and web-forming end of the paper machine to be unrefrigerated and unin- 100 sulated. Under other conditions, however,and this is my, preferred practice of this adaptation of my invention,-I reverse the above procedure and allow the fibrous mix in the concentrated stage to run at the normal temperature, and 105 maintain a low temperature in the mix only when it is in the dilute stage.- Thismay be accom-' plished' by refrigerating the concentrated mix (suitably after its passage from the last container of the system containing the concentrated mix which is usually known as the machine chest, and just before its delivery to the mixing box of the paper machine) and/or refrigerating the circulating machine waters, coupling this if desired with suitable insulation of the instrumentalities for handling the mix at the dilute stage, the machine water handling instrumentalities, and if desired the web-forming device of the paper machine itself.

My preferred practice of this second adaptation of my invention has the advantage that it allows the fibre refining operations, for example the beating and/or jordanning of the mix, to be carried on at ordinary temperatures, thus bringing about a normal hydration of the cellulose, which may under some conditions be retarded at lower temperatures. The prepared mix, at a normal temperature, may be refrigerated just prior to dilution as stated above; but I have found it convenient not to refrigerate this mix but rather only the liquid used to dilute it. Thus this fibrous mix is allowed to arrive, at its normal temperature, at the mixing box, at which point it meets the machine waters, which are normally used to dilute the mix, in refrigerated condition. If other diluting liquids such as fresh water be added at this point, they may also be refrigerated if desired.

The concentration of the fibrous mix as it comes to the mixing box, i. e. the point of dilution, varies somewhat, but for purposes of the illustrative computation given below may be considered to be approximately 4 per cent. solids, while similarly the mix running to the web-forming device, especially in highlyfilled papers, may be considered to have a concentration of solids of approximately 1 per cent. and the circulating machine waters may be considered to have a solid content of approximately one-half of one per cent. It will be apparent that in such case, six parts by weight of circulating machine waters are required for every part by weight of the concentrated mix coming into the mixing box in order to producea dilute mix of 1 per cent. concentration suitable for running off on the webforming device. Under these conditions of course the concentrated mix, although being at ordinary temperatures, will be only one seventh of the total weight of the final dilute mix formed therefrom, and thus if the waters used for diluting the concentrated mix be strongly refrigerated the desired temperature of approximately 10 C., or below, may easily be attained. It will of course be understood that the figures in the above computation are illustrative only and not limiting, as they may vary within wide limits depending on grade of paper run, machine conditions and the like, as is well known in the art.

Of course if the chemically incompatible alkaline filler and acidic material are present in the beater, this particular adaptation of the invention, i. e. refrigerating the dilute stage, will not be particularly serviceable as the deterioration or,

destruction of the acidic material will already have been effected while the mix is in the concentrated condition. However, ths particular adaptation is especially suitable when used in connection with the inventions disclosed in my above referred to patents and applications wherein the minimizing principle is employed; that is, if alkaline filler or acidic material or both be added at the dilute stage to a mix which is of a relatively low temperature at that point, the reaction between these two which is already being minimized by the short time and dilute concentration under which these two materials contact, will be still further minimized by the low temperature at which they contact.

This results in an improvement in the sizing and/or acidic effects desired to be maintained in the presence of the alkaline filler, and results in substantially improved paper made therefrom, a substantially improved machine operation, and diminution of foaming. It may also in certain cases result in economy of chemicals employed such for example as alum.

It is desirable, in order to maintain the low temperature, to have the entire web-forming end of the paper machine, as well as the machine water circulating and dilute stage system, properly insulated. However, because of the expense involved thereby, it is sometimes satisfactory merely to insulate the dilute system up to the point of web formation-or even if desired to leave the machine screens and/or head box uninsulated,as by such means substantial economy of insulating media is effected, and also accessibility of the screens and machine headbox is retained.

While the adaptation of the invention involving only dilute stage refrigeration may be carried out by refrigeration of the diluted fibrous mix itself, the simplest method to employ is to refrigerate in any suitable known manner only the machine water, i. e. chiefly tray water, returning to the mixing box. This reduces the amount of refrigeration equipment and accessories to a minimum, permits the refrigeration of a liquid of low solid content and provides a satisfactory, simple and economical method of carrying out my invention. It is desirable as will be apparent to insulate the mixing box, rifilers, the tray water cycle means and the like, as well as the associated piping, in order to avoid the abstraction of heat from the surroundings by the refrigerated material. I

To summarize, then, a most economical and convenient way to carry out this adaptation of my invention is to insulate the rifliers (if the paper machine be thus equipped), and the tray water pump and piping, and to subject the tray waters to refrigeration at a suitable point between the point of their leaving the paper machine and the point of their delivery to the mixing box.

In the manufacture of unsized papers filled with alkaline filler foaming is substantially reduced, or eliminated in some cases, by the employment of my method. In some cases, particularly in unsized papers, where it is desired to run a closed or nearly closed white water system, but where this ideal could not hitherto be attained owing to increase of foaming when the system became nearly closed, such system may now be run owing probably to the diminution of the action (because of the substantially reduced temperature of the system) between the alkaline filler and the foam-forming constituents which accumulate in a closed white water system.

When I speak of refrigeration in referring to a -mix or any component of a mix, I mean the lowering of the temperature thereof substane tially below that at which it normally occurs in mill operation, by the extraction of heat therefrom. Any suitable means may be used for this purpose, such for example as spray systems. cooling towers, systems cooled by the passage through pipes of circulating cold water, or any of the known artificial refrigeration systems (for a good summary of which see the chapter on refrigeration in Kent's Mechanical Engineers Handbook, John Wiley & Sons, Inc., N. Y.). Preferably the means employed should not contaminate or substantially dilute the medium being refrigerated. Where an adequate supply of circulat ng natural cold water is available (such as in the northern lakes or on the seaboard in winter) such may be used as a refrigerating fluid,

but in many cases artificial refrigeration will be found the best and most easily regulated means.

It is apparent that in using the expressions minimizing the temperature or refrigerating in referring to a mix or any component thereof, I do not refer to the substantially inconsequential reduction of temperature of the mix brought about by adding constituents at the temperature at which they would normally occur in mill operation. For example, it is customary practice to add water from a mill water supply at various points in a fibrous mix preparation system. It frequently happens that such water is of a lower temperature than the mix to which it is added, but the quantities added and the temperature prevailing are such as not to produce a temperature in the resulting mix which, from the standpoint of this invention, can be considered as materially lowered, and such well known practice of course I do not include Within the scope of my invention.

Where I use the term alkaline filler, I mean substantially water insoluble filler which when agitated in contact with freshly boiled distilled water, say for an hour, will impart a pH value to such water greater than 7.0, that is, which will be on the alkaline side of the neutral point. Among the fillers included in this group may be mentioned calcium carbonate, of which lime mud from the causticizing process is one form; calcium carbonate magnesium basic carbonate employed in the paper disclosed in my U. S. Patent No. 1,595,416, issued August 10, 1926; calcium carbonate magnesium hydroxide disclosed in my U. S. Patent No. 1,415,391, issued May 9,1922; and other substantially water insoluble normal or basic carbonates of alkaline earth metals (which expression is herein intended to include magnesium) or compounds, double salts, or physically associated mixtures of these with one or more other acid soluble materials of a substantially water insoluble nature.

By the term alkaline filler I also intend to include fibrous material and/or other material such as paper coating constituents or the like containing one or more compounds of the character referred to, such as old papers or similar papers, broke, or the like.

When I use the word paper herein, I use it in the broad sense to include products of manufacture of all types and of all weights and thicknesses, which contain as an essential constituent a considerable amount of prepared fibre and which are capable of being produced on a Four-- drinier, cylinder, or other forming, felting, shaping or molding machine.

While I have described in detail the preferred embodiment of my invention, it is to be understood that the details of procedure, the proportions of ingredients, and the arrangement of steps and equipment may be widely varied without departing from the spirit of my invention or the scope of the subjoined claims.

I claim:

1. In the manufacture of paper filled with alkaline filler, the improvement which comprises refrigerating the aqueous fibrous mix"from which said paper is made at a point prior to that at which the web formed from said mix passes from the web-forming device.

2. In the manufacture of paper filled with alkaline filler, the improvement which comprises refrigerating a component of the aqueous fibrous mix from which said paper is made at a point prior to that at which the web formed from said mix passes from the web-forming device.

3. In the manufacture of paper filled with alkaline filler, the improvement which comprises 5 line fillerythe improvement which comprises refrigerating the aqueous fibrous mix from which said paper is made at a point subsequent to the passage of said mix from the machine chest.

6. In the manufacture of paper filled with alka- 7, line filler, the improvement which comprises re- 1'00 frigerating the aqueous fibrous mix from which said paper is made when said mix is at the dilute stage of the paper making process.

7. In the manufacture of paper filled with alkaline filler, the improvement which comprises refrigerating a component of the dilute aqueous fibrous mix from which said paper is made.

8. In the manufacture of paper filled with alkaline filler, the improvement which comprises refrigerating thepaper machine water which is the concentrated aqueous fibrous mix from which said paper is made.

9. In the manufacture of paper filled with alkaline filler, the improvement which comprises refrigerating the paper machine tray water.

10. In the manufacture of paper filled with alkaline filler, the improvement which comprises maintaining the aqueous fibrous mix from which said paper is made, subsequent to the fibre refining operations performed on said mix, at a temperature not substantially in excess of 10 C.

11. In the manufacture of paper filled with alkaline fi1ler,',the improvement which comprises maintaining the aqueous fibrous mix from which said paper is made, subsequent to the passage of said mix from the machine chest, at a temperature not substantially in excess of 10 C.

12. In the manufacture of paper filler with alkaline filler, the improvement which comprises maintaining the aqueous fibrous mix from which said paper is made, at the dilute stage of the paper making process, at a temperature not substantially in excess of 10 C.

13. The process of manufacturing paper filled with alkaline filler which comprises preparing a fibrous mix in a concentrated aqueous condition, refining the fibre-of said mix, diluting said mix with refrigerated tray water from a paper machine, running the resulting dilute aqueous fibrous mix over a web-forming device, and drying the resulting web.

14. In the manufacture of paper from an aqueous fibrous mix containing alkaline filler and material which is chemically incompatible therewith, the improvements which comprise refrigerating said mix, and adding at least one of said chemically incompatible constituents under conditions favoring the minimizing of the time of contact of the constituents of said mix. 150

15. In the manufacture of paper from an aqueous fibrous mix containing alkaline filler and material which is chemically incompatible therewith, the improvements which comprise refrigerating said mix, and adding at least one of said chemically incompatible constituents under conditions favoring the minimizing of the time and intimacy of contact of the constituents of said mix.

16. In the manufacture of paper from an aqueous fibrous mix containing alkaline filler and material which is chemically incompatible therewith and wherein at least one of said chemically incompatible materials is added at the dilute stage of the paper making process, the improvement which comprises maintaining the dilute aqueous mix from which said paper is made in refrigerated condition.

17. In the manufacture of paper filled with alkaline filler wherein alum is added at the dilute stage of the paper making process, that step comprising maintaining the dilute aqueous mix from which said paper is made in a refrigerated condition. I

18. In the manufacture of paper filled with alkaline filler, wherein alum and alkaline filler are added at the dilute stage of the paper making process, that step comprising maintaining the dilute aqueous mix from which said paper is made in a refrigerated condition. I

19. In combination: fibre refining apparatus and associated equipment for preparing an aqueous papermaking mix for delivery to a web-forming device; a web-forming device; and refrigerating means adapted for extracting heat from said aqueous paper making mix.

20. In combination: fibre refining apparatus and associated equipment for preparing an aqueous papermaking mix for delivery to a webforming device; a web-forming device; and refrigerating means adapted for extracting heat from a component of said aqueous papermaklng mix.

21. In combination: a papermaking machine including means for diluting a concentrated aqueous papermaking mix and handling the resultant dilute mix, and a web-forming device; means for cyclically returning water passing through said web-forming device to said concentrated mix diluting means; and means for refrigerating said cyclically returned water.

22. A system comprising fibre refining apparatus and associated equipment for preparing an aqueous papermaking mix for delivery to a web-forming device and a web-forming device, characterized by the fact that at least part of said system is insulated against the absorption of heat from the surroundings.

23. In combination: a system comprising fibre refining apparatus and associated equipment for preparing an aqueous papermaking mix up to point of delivery of said mix to a web-forming device and a web-forming device, characterized by the fact that at least part of said system is insulated against the absorption of heat from the surroundings; and refrigerating means.

HAROLD ROBERT RAFTON. 

